Ca-induced phase transition at 150 K in Y1−xCaxBa2Cu4O8 single-phase high-Tc superconducting material
Wu Ting, O.-M. Nes, T. Suzuki, M. G. Karkut, K. Fossheim, Y. Yaegashi, H. Yamauchi, S. Tanaka
DOI 10.1103/PhysRevB.48.607 · Physical Review B
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Abstract
Elastic and specific-heat measurements have been performed on single-phase polycrystalline Y1−xCaxBa2Cu4O8 (x=0, 0.025, 0.05, 0.1) in the temperature region from 100 to 180 K. Anomalies are detected in elastic and specific-heat measurements at 150 K for Ca-doped specimens. A reversible steplike change in sound velocity accompanied by an attenuation peak is observed in material with x=0.1 doping at 150 K on cooling and heating, for both longitudinal and transverse modes. These elastic anomalies have a clearly observable counterpart in the specific heat. The anomalies in elastic and specific-heat measurements show dominantly the character of a mean-field-type phase transition. We observe similar anomalies at the same temperature even for x=0.025 and 0.05, while for pure YBa2Cu4O8 samples no anomalies are found in this temperature region. Thus we find a Ca-induced, but concentration-independent, transition temperature in the available range of x values. No magnetic anomaly is found by ac magnetic susceptibility. The transition is proposed to be of a structural type although x-ray powder diffraction did not reveal the origin.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu4O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 76 | Pressure not reported | onset |
| Y0.975Ca0.025Ba2Cu4O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 82 | Pressure not reported | onset |
| Y0.95Ca0.05Ba2Cu4O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 87 | Pressure not reported | onset |
| Y0.9Ca0.1Ba2Cu4O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 89 | Pressure not reported | onset |
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